I am the great-great granddaughter of slaves. My dentist father chose to raise his family in New England rather than remain in Virginia, where he and his sisters had walked picket lines as young children in the 1930s, where their school books were grime-caked castoffs from white schools, where a C or an N would appear after his name in the telephone book because his brown hand would be unacceptable inside a white jaw.

I am the highly educated child of highly educated parents, a lifelong desegregater who has always lived in comparative comfort, but I have always lived with the same otherness as my less fortunate brothers and sisters. I have been called jigaboo, jungle bunny and nigger bitch. At the schools of Stamford, Connecticut, at Harvard University, and on Hollywood filmsets, I have encountered social and cultural apartheid as well as disbelief and hostility that someone such as me could even exist.

But three years ago when he was seven, my sister's blond, blue-eyed mixed-race child put his arm next to mine and cheerfully said, "I'm white and you're brown, it doesn't mean anything but it's really important."

Otherness is an exhausting and exasperating undercurrent that can and often does turn toxic. The ascension of Barack Obama by means of intellect and wisdom rather than physical or musical prowess, the example of his fierce, grounded and equally intelligent wife and their two daughters, deals a mighty blow to racial assumptions. They are all these things and they are black folks. We people of colour know that Obama's colour is not an accessory but the crucible in which his extraordinary character has been honed, the strength from which he will sagely govern. Most of us never believed that we'd see this in our lifetimes and with our tears of pride and joy we are dancing.

After reading his memoir Dreams from My Father in the last months of 2006, I recognised in Obama a man of extraordinary qualities and on the day he declared his candidacy for president of America I joined my lot with his, believing that the presidency of such a man might enable the United States to unstick itself and even transcend the mire into which it had descended. To my mind his combination of intellect, charisma, empathy and grit made him a superb candidate for any time and certainly the best for these trying times. He was all of these things, and he was black.

The vast majority of my campaign colleagues over these 21 months have been whites who saw in Obama the same qualities as I did. Their numbers swelled as the campaign progressed from hundreds to thousands to tens and eventually hundreds of thousands. They were the engine of Obama's successful campaign; without their work in Iowa and New Hampshire, the vast majority of African-Americans would not have thought an Obama presidency as other than fantasy. Their shouts were as heartfelt as their exemplary dedication, but they didn't, they couldn't feel as I did when that disembodied voice in Chicago's Grant Park announced: "Ladies and gentlemen, the president-elect of the United States of America". It was 5am. Alone by choice in my north London home, I screamed at the top of my lungs and when I saw Barack Obama and his beautiful African-American family take the stage I commenced to heave and sob.